Manufacturing of semiconductor devices commonly requires deposition of electrically conductive materials on semiconductor wafers. The conductive material, such as copper, is often deposited by electroplating onto a seed layer of metal deposited onto the wafer surface by a physical vapor deposition (PVD) or chemical vapor deposition (CVD) method. Electroplating is a method of choice for depositing metal into the vias and trenches of the wafer during damascene and dual damascene processing. To meet the demands of modern semiconductor processing, the electrically conductive material deposited on the surface of a semiconductor wafer needs to have the lowest possible defect density.
Damascene processing is a method for forming interconnections on integrated circuits (ICs). It is especially suitable for manufacturing integrated circuits, which employ copper as a conductive material. Damascene processing involves formation of inlaid metal lines in trenches and vias formed in a dielectric layer (inter-metal dielectric). In a typical damascene process, a pattern of trenches and vias is etched in the dielectric layer of a semiconductor wafer substrate. Typically, a thin layer of an adherent metal diffusion-barrier film such as tantalum, tantalum nitride, or a TaN/Ta bilayer is then deposited onto the wafer surface by a PVD method, followed by deposition of electroplate-able metal seed layer (e.g., copper, nickel, cobalt, ruthenium, etc.) on top of the diffusion-barrier layer. The trenches and vias are then electrofilled with copper, and the surface of the wafer is planarized. Other types of electroplating processes may include wafer level packaging (WLP) and through-silicon-via (TSV) processes, for example.
A typical electroplating apparatus includes a reaction vessel that houses electrolyte, a substrate (which acts as the cathode) and an anode. Certain electroplating systems employ a porous barrier between the substrate and the anode. This barrier is often, but not always, a cationic exchange membrane which permits the passage of small positively charged species and blocks the passage of negatively charged species and any relatively large species. One advantage to using a membrane between the anode and substrate is that different chemistries may be used for the anolyte and catholyte. For example, it may be desirable to include certain plating additives (e.g., organic plating additives such as accelerator, suppressor and leveler) in the catholyte, while maintaining the anolyte free of such additives. It is generally desirable to ensure that the anolyte does not include plating additives in order to prevent the additives from coming into contact with the anode where they may be degraded to form defect-inducing species.
Unfortunately, in certain cases the membrane can adsorb species present in the catholyte (and/or anolyte in some cases). This blockage by adsorption can lead to the failure of an electroplating process. As such, there exists a need for an improved membrane that better resists becoming blocked.